1. Field of the Invention
This invention relates to a process and apparatus for producing a ceramic material. This invention particularly relates to a process and apparatus for producing a ceramic material, wherein aerosolized raw material particles are jetted out and wherein the raw material particles are thereby deposited on a substrate to form a molded body.
2. Description of the Related Art
Heretofore, injection molding techniques have been utilized as the techniques for producing ceramic materials. With the injection molding techniques, though complicated molded bodies are capable of being molded accurately, mixing proportions of organic binders with respect to molding materials are as high as approximately 50% by weight. Therefore, expansion and contraction differences of the molded bodies at the time of degreasing steps are large. In order for cracking due to the expansion and contraction differences to be prevented, it is necessary to perform the degreasing steps for a long period of time while distributions of temperatures of the molded bodies are being kept to be small at markedly low temperature rising rates.
For example, in Japanese Unexamined Patent Publication No. 6(1994)-279127, there has been proposed a degreasing step, wherein heating from inside regions of molded bodies is performed by microwave heating and wherein the distributions of temperatures within the molded bodies are kept to be small. However, in the cases of materials, such as PZT and BaTiO3, which have large dependency of a dielectric loss upon temperatures and which have a low thermal conductivity, there is the risk that nonuniform temperature distributions will arise, and that local heated regions will melt due to a runaway phenomenon in which microwave energy concentrates at local regions.
Also, for example, in Japanese Unexamined Patent Publication No. 2007-162077, an aerosol deposition (AD) technique utilizing shock compaction phenomenon of solid particles has been disclosed as a process for producing a ceramic material. The disclosed AD technique has attracted particular attention. Specifically, with the AD technique, an aerosol containing raw material particles dispersed in a carrier gas is jetted out from a nozzle toward a substrate, the raw material particles are deposited on the substrate, and a molded body is thereby formed. With the AD technique, the raw material particles are bound firmly to one another by the shock compaction phenomenon, and therefore the use of organic binders is suppressed.
However, with the rapid advances made in development of devices related to micro electro-mechanical systems (MEMS) in recent years, there has arisen a strong demand for formation of fine structures and integration of devices, such as laminated ceramic capacitors and piezoelectric actuators. Also, there is a strong demand for suppression of the use of organic binders such that discharging of the organic binders in the degreasing steps as greenhouse gases may be prevented from the view point of environmental loads, and such that the consumption of energy for long-time heating in the degreasing steps may be prevented.
With the technique disclosed in Japanese Unexamined Patent Publication No. 6(1994)-279127, in order for the ceramic material having the complicated shape to be molded as described above, it is necessary for a comparatively large quantity of organic binders to be added for enhancement of fluidity.
With the technique disclosed in Japanese Unexamined Patent Publication No. 2007-162077, though the use of the organic binders is suppressed, it is not always possible to mold the ceramic material having the complicated shape.